Mycobacterium tuberculosis-Specific T-Cell Responses Are Impaired During Late Pregnancy With Elevated Biomarkers of Tuberculosis Risk Postpartum

Abstract

Background: Pregnancy is a risk factor for progression from latent tuberculosis infection to symptomatic tuberculosis. However, how pregnancy influences T-cell responses to Mycobacterium tuberculosis is unknown.

Methods: We measured M. tuberculosis-specific cytokines, T-cell memory markers, and overall CD4+ and CD8+ T-cell activation by flow cytometry from 49 women (18 with and 31 without HIV) who became pregnant while enrolled in a randomized controlled trial of preexposure prophylaxis for HIV. We analyzed data using COMPASS, an established statistical method for evaluating overall antigen-specific T-cell responses.

Results: Pregnant women with latent tuberculosis infection demonstrated significantly diminished M. tuberculosis-specific CD4+ cytokine responses in the third trimester (COMPASS polyfunctional score [PFS], 0.07) compared before (PFS, 0.15), during (PFS, 0.13 and 0.16), and after pregnancy (PFS, 0.14; P = .0084, Kruskal-Wallis test). Paradoxically, M. tuberculosis-specific CD8+ cytokines and nonspecifically activated T-cells increased during late pregnancy. Nonspecific T-cell activation, a validated biomarker for progression from latent tuberculosis infection to tuberculosis disease, increased in latent tuberculosis infection-positive women postpartum, compared with latent tuberculosis infection-negative women.

Conclusions: Pregnancy-related functional T-cell changes were most pronounced during late pregnancy. Both M. tuberculosis-specific T-cell changes during pregnancy and increases in immune activation postpartum may contribute to increased risk for tuberculosis progression.

Clinical trials registration: NCT0557245.

Trial registration: ClinicalTrials.gov NCT00557245.

Keywords: M. tuberculosis; T cells; T-cell activation; T-cell memory; pregnancy.

© The Author(s) 2021. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mail: journals.permissions@oup.com.

Figures

Figure 1.

Baseline immune characteristics are stable across pregnancy. A, Flowchart of stored sample selection of participants with incidental pregnancies in the Partners PrEP study. B, Fold change of the proportion of CD4+ T cells expressing IFN-γ after incubation with ESAT-6 and CFP-10 pooled peptides, compared to vehicle control. C, COMPASS functional score and polyfunctional score stratified by latent tuberculosis infection status. D, Proportion of CD4+ T cells and CD8+ T cells, stratified by pregnancy trimester and HIV status. Prepregnancy sample, n = 49; 1st trimester, n = 9; 2nd trimester, n = 14; 3rd trimester, n = 24; postpartum, n = 22. Circles indicate HIV-negative study participants, while triangles indicate WLWH. Bars indicate median values. ∗Among participants with pre-pregnancy and pregnancy samples only. ∗∗Includes one participant with a sample collected during pregnancy < 20 weeks of gestation without an evaluable postpartum sample. ∗∗∗Includes two participants with two samples collected during pregnancy. Abbreviations: HIV, human immunodeficiency virus; IFN-γ, interferon-γ; LTBI, latent tuberculosis infection; PBMC, peripheral blood mononuclear cell; PrEP, preexposure prophylaxis; WLWH, women living with HIV.

Figure 2.

Mycobacterium tuberculosis-specific CD4+ T-cell responses are diminished during the third trimester of pregnancy. A-B, PFS (A) and FS (B) generated from COMPASS analysis of CD4+ T cell responses, stratified by pregnancy trimester. C-D, PFS (C) and FS (D) generated from COMPASS analysis of CD8+ T cell responses, stratified by pregnancy trimester. Circles indicate an HIV-negative study participant, while triangles indicate a WLWH. Bars indicate median values, Kruskal-Wallis test. Column-to-column comparisons are made with Dunn test. Abbreviations: FS, functional score; HIV, human immunodeficiency virus; PFS, polyfunctional score; WLWH, women living with HIV.

Figure 3.

PMA/ionomycin-stimulated CD4+ T-cell cytokine responses are dynamic across pregnancy. A, Proportion of IL-2+CD4+, TNF+CD4+, or IFN-γ+CD4+ T cells stratified by pregnancy trimester. B, Proportion of IL-2+CD8+, TNF+CD8+, and IFN-γ+CD8+ T cells stratified by pregnancy trimester. Black dots indicate an HIV-negative study participant, while gold triangles indicate an HIV-positive study participant. Bars indicate median values. P values calculated by Kruskal-Wallis test. Column-to-column comparisons are made with Dunn test. Abbreviations: HIV, human immunodeficiency virus; IFN-γ, interferon-γ; IL-2, interleukin 2; TNF, tumor necrosis factor.

Figure 4.

The proportion of Mycobacterium tuberculosis-specific naive effector memory T cells decreases during the third trimester of pregnancy. A, Overall proportion of Tem (CCR7−CD45RA−) among all cytokine-producing CD4+ T cells after restimulation with ESAT-6 and CFP-10 antigens, stratified by pregnancy status. Black dots indicate an HIV-negative study participant, while gold triangles indicate a sample from WLWH study participant. P values calculated by Kruskal-Wallis test. Column-to-column comparisons are made with Dunn test. B, Pie chart of Boolean-gated T helper memory phenotype frequencies, comparing the third trimester with other time points, connected by overhead bar. Arc: blue, CCR7+ cells; red, CD45RA+ cells. Pie slice: red, naive CD4+ T cells; blue, Tem CD4+ T cells; gray, Tcm; white, TEMRA cell. Signifcance determined by permutation test of 10 000 iterations. Abbreviations: HIV, human immunodeficiency virus; Tcm, central memory T cell; Tem, effector memory T cell; WLWH, women living with HIV.

Figure 5.

Nonspecific T-cell activation increases during pregnancy and latent tuberculosis infection-positive women demonstrate increased T-cell activation postpartum. A and B, Proportion of (A) HLA-DR+CD38+CD4+ T cells and (B) HLA-DR+CD38+CD8+ T cells stratified by pregnancy status. C and D, Proportion of (C) HLA-DR+CD38+CD4+ T cells from samples collected prepregnancy and (D) proportion of HLA-DR+CD38+CD4+ T cells from samples collected postpartum stratified by latent tuberculosis infection status of the participant. Circles indicate an HIV-negative study participant, while triangles indicate sample from WLWH. Bars indicate median values. P values calculated by Kruskal-Wallis test. Column-to-column comparisons are made with Dunn test in multiple group comparisons or Mann-Whitney U test for tests between 2 groups. Abbreviations: HIV, human immunodeficiency virus; LTBI, latent tuberculosis infection; WLWH, women living with HIV.